Traditionally, as shown in FIG. 2, a tube expander for expanding tubes used for a heat exchanger has a structure that includes a ceiling 52 mounted on top of a pair of support columns 51 that are vertically affixed to a base 50, a cylinder 53 that is attached to the ceiling 52, and an operation plate 54 assembled with a plurality of tube expansion mandrels 55 that are vertically movable for expanding the tubes by expansion and contraction movements of the cylinder 53.
Since each tube expansion mandrel 55 is formed in the shape of a rod with a relatively small diameter and a sufficient length to fit-in the diameter and length of each tube of the heat exchanger (not shown) positioned on the base 50, the tube expansion mandrels 55 need to be supported at proper locations to restrict any flexures in horizontal directions during the press-fitting operation.
Therefore, in order to restrict such flexures of the mandrels, the tube expander further has a plurality of guide plates 56 that are located under the operation plate 54. Each of the guide plates 56 has a plurality of through holes for the tube expansion mandrels 55 to pass therethrough. The tube expander further includes tubular strippers (not shown) on the bottom side of the lowest guide plate 56 (the side facing the base 50) that fit over the tubes protruding from the surface of the heat exchanger (not shown) and press the surface down to adjust the length of the tubes, and an end plate 57 also consisting of a plurality of through holes for the tube expansion mandrels 55 to pass therethrough.
Further, at each left end and right end of the operation plate 54, the guide plate 56 and the end plate 57, a pair of guide bars 58 affixed between the base 50 and the ceiling 52 are inserted therethrough at the centers in the front and back direction. Thus, the operation plate 54, the guide plate 56, and the end plate 57 are able to vertically move along the guide bars 58 while maintaining a parallel relationship with each other.
Further, hang bolts 59 (not shown on the right side of drawing) are inserted in the operation plate 54, the guide plate 56, and the end plate 57, respectively. By the engagement of heads 59a attached to both ends of each hang bolt 59 which prevent the hang bolt 59 from falling out, the maximum distance between the operation plate 54, the guide plate 56, and the end plate 57 is determined.
Further, in the operation plate 54, the guide plate 56, and the end plate 57, a pair of ball screws 60 parallel to the guide bars 58 are inserted therethrough, where the bottom ends thereof are movably supported by the end plate 57.
On each of the ball screws 60, an upper stopper 61 is rotatably attached thereto, and on each of the upper stoppers 61, a half-sized arc that contacts with a half of the cylindrical arc of the guide bar 58 (guide post) is formed. Thus, when the ball screw 60 is rotated by a drive unit such as a motor (not shown), the half-sized arc slides along the guide bar 58 while the upper stopper 61 itself moves in an up-and-down direction along the ball screw 60.
The upper stopper 61 is able to contact the bottom surface of the operation plate 54 upon passing through a long hole 56a formed on the guide plate 56.
Further, between the base 50 and the end plate 57, lower stoppers 62 are established for adjusting the length of the tubes projecting from the end surface of the heat exchanger by restricting the downward movement of the end plate 57.
On the front side of each of the lower stoppers 62, the guide bar 58 is inserted therein, and the rear side thereof is slidably attached to the guide rail 63 which is fixedly formed on the column 51.
Further, between the guide bar 58 and the guide rail 63, the lower stopper 62 is rotatably attached therein, and a bottom end of a ball screw 64 which is parallel to the guide bar 58 and the guide rail 63 for vertical movement is rotatably supported on the base 50.
Therefore, when the ball screw 64 for vertically moving the lower stopper 62 rotates by a drive unit such as a motor (not shown), the lower stopper 62 smoothly moves in an up-and-down direction through the guide bar 58 and the guide rail 63 without sway.
The lower stopper 62 formed in the structure noted above can restrict (stop) the downward movement of the end plate 57 by contacting with the bottom surface of end the plate 57 that moves downwardly along with the operation plate 54 when the cylinder 53 is extended.
However, in the tube expander having the above noted conventional structure, the left and right ends of the operation plate 54, the guide plate 56, and the end plate 57 are inserted with a pair of guide bars 58 at about the centers in the front and back direction and are slidably supported by the guide bars 58.
In other words, in order to smoothly move each of the above noted plates along the guide bars 58 while maintaining a parallel relationship with one another, the guide bars 58 must be inserted through the centers (with respect to the front and back direction of the tube expander) of each of the plates.
Consequently, the guide bars 58 inevitably block the left and right sides of the base 50, and since various oil pressure units and control boards (not shown) are usually installed on the back side of the tube expander, the heat exchanger can only be transported in and out of the front side (arrow P) of the tube expander during the tube expansion operation.
As a result, when organizing a production line of the heat exchanger to improve the productivity, the transportation of the heat exchanger into the tube expander or out of the tube expander to another location or toward another device must be conducted in the left and right direction (arrow Q). However, due to the reason noted above, a reciprocable point has to be formed on the transportation path (reciprocating transportation path), thus, creating various problems such as a lower transportation efficiency as well as a need for a special transportation mechanism for that reciprocable point, which increases the production cost for the tube expander.